In order to explore the pathogenesis of experimental brain tumors as a basis for a better understanding of the pathogenesis of human brain tumors, the selective neurotropic carcinogens, ethylnitrosourea and methylnitrosourea, will be used to induce gliomas in inbred Fischer rats. The tumors will provide the material for in vivo and in vitro studies of cell-mediated immunity and humoral immune factors associated with nervous system neoplasms. By using well-established histologic, transplantation, lymphocyte isolation, and tissue culture techniques including the microcytotoxicity assay, it is proposd to carry out investigations aimed as follows: (1) To test for the presence of cell- mediated immunity, blocking and arming serum factors in rats carrying intracerebral or subcutaneous transplants of nitrosourea-induced gliomas. (2) To measure serum blocking factors and arming in rats which develop nitrosourea-induced gliomas. (3) To examine whether serum unblocking factors, potentiation and arming arise in rats which receive intracerebral or subcutaneous glioma transplants that are caused to regress by radiation or surgical excision. (4) To test whether the cerebrospinal fluid of glioma-bearing rats carries factors for blocking, unblocking, potentiation and arming. (5) To test if adoptive cell- mediated immunity of syngeneic rats against nitrosourea-induced gliomas can be demonstrated, (6) To investigate if the clinical course and morphological aapearances of transplanted gliomas can be affected by the administration of regressor serum. (7) To examine whether nitrosourea- induced gliomas possess tissue-type-specific tumor antigens which cross react with one another in in vivo and in vitro systems.